Ph.D.: University of California at Berkeley
Postdoctoral Training: University of California at Berkeley
Honors: National Institutes of Health Independent Scientist Award

Development of Neural Sex Differences; Hormones and Neurotrophic Factors

During mammalian development an initially bi-potential embryo undergoes differentiation to become male or female. This process proceeds primarily under the control of gonadal steroid hormones and includes sexual differentiation of the nervous system. Work in this lab is focused on understanding how steroid hormones influence neural development.

We study a simple neuromuscular system which is sexually dimorphic in many mammals, including humans. Motor neurons of the spinal nucleus of the bulbocavernosus (SNB) reside in the lumbar spinal cord and innervate striated muscles attached to the phallus. Adult males have many more SNB motoneurons than do females, and the sex difference comes about as a result of hormone-regulated cell death. SNB motoneurons and their target muscles initially develop in both sexes. Testosterone keeps the muscles and motoneurons alive in males, while they degenerate in females. The SNB neuromuscular system of a female rat can be completely masculinized by treating her with androgens around the time of birth.

We have found that, like androgens, ciliary neurotrophic factor (CNTF) can rescue SNB motoneurons and their target muscles in newborn female rats. In addition, the normal sex difference in the spinal cord does not develop in mutant mice lacking the CNTF receptor. We are currently exploring the hypothesis that CNTF, or other trophic factors, mediate the effects of androgens in the developing SNB neuromuscular system.